Formula and method
Percentage of a value = (percentage ÷ 100) × value. Percent change = ((new − original) ÷ |original|) × 100.
Worked example
20% of 150 is (20 ÷ 100) × 150 = 30.
Assumptions
- Percent change from an original value of zero is undefined.
- Negative values are supported.
Reference sources
Reviewed and updated 2026-07-14